The late Salvador Dali, the surrealist Spanish artist notorious for commercial opportunism, might well have laughed and twirled his moustache at the latest dispute over the lucrative use of his name.

Scores of bronze "Dali" sculptures, some priced at more than £1m, are currently on sale to wealthy City traders by a millionaire Italian art dealer, Beniamino Levi. His London exhibition is just a small part of an international Dali sculpture empire estimated to be worth more than £60m.

A Guardian investigation has found the sculpture industry, known in the trade as "Almost Dali", has ballooned worldwide since the celebrated Spanish painter's death in 1989, but is now under investigation.

The official Salvador Dali foundation says many of the sculptures are simply not works of art. Levi disagrees: he says the foundation is just "very jealous" of his success.

Joan Manuel Sevillano, who heads the Spanish government-backed Gala-Dali Foundation in Madrid, says it is investigating the way the multiple editions of sculptures attributed to Dali are being marketed in their thousands.

"You look at the sculpture and you don't know what you are seeing," he said. "We are concerned about using the name of Dali inappropriately. We are not talking about pieces which are classified as works of art. These are commercial sculptures, made for decorative purposes."

Levi, interviewed at his parallel Dali exhibition in Paris this week, insisted his sculptures were indeed art.

Although they were not made by Dali, Levi said he had purchased the rights to turn images taken from certain Dali drawings into sculptures. The rights had been bought by him in the 1980s from the ailing Dali's then-secretary and business manager, Enrique Sabater, he said.

A 5-metre high statue of Alice in Wonderland, towering over passersby at London's Moor House gallery, is offered for sale at more than £1.5m, along with smaller bronzes costing £20,000 upwards.

Smaller versions of the Alice come in multiple editions of more than 1,000, in blue, green and brown versions. But some of the Alices have been cast as recently as 2005, many years after the painter's death. None come from a model produced by Dali's own hand.

Levi says that, according to the documents supplied by Sabater, Dali approved of the Alice sculpture, based on a 1977 drawing. "This paper says that this plaster was made in Spain and Italy, and Dali approved it. I don't know: I was not there."

He declined to show the Guardian details of his original contract or the foundry records showing how many multiple Dali sculptures had been manufactured and sold since the painter's death.

At the official Dali foundation, Sevillano said: "I just don't know who counts and evaluates the sizes of the editions. They are not submitted to our control."